First, remove the brakeman's cabin. Fairly straightforward - unscrew the cabin from the end wall, and unscrew the deck from the chassis. Then build a new end rail/stanchion assembly, together with some in fill decking to cover the area where the cabin stood.
Spray the whole lot a suitable brown, and varnish to match the LGB colours... Humbrol 160, if you're interested.
Fix to the wagon in place of the original, and you have a variation on the standard LGB theme for a few hours work.